LD 350-1

LD 350-1 is a partial adult left mandible including the canine, both premolars, and all three molars. In terms of overall size, the specimen is within the range of what is seen in small Australopithecus afarensis specimens, and LD 350-1 seems to be a transitional form between Australopithecus and Homo. However, the specimen's anatomy strongly diverges from australopithecines and more closely aligns with Homo: the mental foramina are not located on a depression, it has a symphyseal keel (a line of bone jutting out at the midline of the jaws), the jawbone maintains a more or less constant depth whereas it is deepest under the premolars in some Australopithecus, and there are several differences regarding the tooth crowns. This specimen confirms that Homo dental and jaw anatomy diverged from those of Australopithecus very early on. LD 350-1, like other archaic humans, seems to have lacked a distinct chin. ==Classification==

The origin of Homo 2.8–2.5 mya is accompanied by climatic changes, but because other Homo specimens are not known from this time period, it is unclear if this was indeed the causal factor. The KNM-ER 5431 specimen (comprising left and right premolars and the first two molars) from Koobi Fora, Kenya, dating to 3–2.7 mya could represent the same species as LD 350-1. The discovery of such an early Homo specimen discredits some past hypotheses on the timing of the Australopithecus/Homo transition, including deriving 2.6 mya from A. garhi. It is unclear if A. afarensis, which is known from the same region until 3 mya, was an ancestor of LD 350-1. ==Culture==

tools from Ledi-Geraru, Afar Region, Ethiopia In 2019, the earliest Oldowan stone tools were discovered in Ledi-Geraru dating to 2.6 mya and may have been manufactured by the same species as LD 350-1. The invention of the sharp-edged Oldowan may be tied to unique biological changes in Homo. It is unclear if the Oldowan developed independently or from earlier, simpler australopithecine stone traditions (the only one identified is the Lomekwi industry). In either case, the transition to sharper tools would have allowed different feeding strategies and the ability to process a wider range of foods than australopithecine technology permitted, which would have been advantageous in the changing climate of the time. LD 350-1 lived in a much drier and more open environment than A. afarensis typically inhabited. ==See also==